1. Field of the Invention
The present invention generally relates to resonating nanotubes, more specifically to resonant frequency tunable nanotubes, and still more specifically to resonant frequency tunable carbon multiwall nanotubes (MWNT).
2. Description of the Relevant Art
Nanoscale resonators, with their low masses, low force-deflection spring-rate constants, and high resonant frequencies, are capable of weighing single bacteria [ILIC 00], detecting single spins in magnetic resonance systems [RUGA 04], and even probing quantum mechanics in macroscopic systems [LAHA 04], [BRES 02]. These resonators are typically created from surface-micromachined silicon; however, carbon nanotubes provide an alternate, nearly ideal building material because of their low density, high Young's modulus, and atomically perfect structure. Already there has been much progress in analyzing and constructing nanotube-based resonators [LI 04], [SAZO 04].
Present designs typically either operate at a single frequency or have a relatively narrow frequency range, possibly imposing limitations in their application.
These resonators are typically micromachined from silicon; however, because of their low density, high Young's modulus, and atomically perfect structure, carbon nanotubes provide an alternate, nearly ideal building material. Some progress has been made in constructing nanotube-based resonators [SAZO 04]. However, these resonators have a narrow frequency range and obey a relatively complicated physical model.
U.S. Pat. No. 6,709,566, hereby incorporated by reference describes a method for shaping small three-dimensional articles such as nanotubes exhibiting a layered structure through material removal such that the article is controllably shaped to exhibit a desired contour. Typically, material removal does not require use of a chemical etchant and is carried out while the article and a shaping electrode are positioned in contact material removal relationship with under a potential difference. The invention also relates to nanotubes and small three-dimensional articles exhibiting a layered structure having a controllably shaped contour.
U.S. Pat. No. 6,803,840, hereby incorporated by reference describes a tunable nanomechanical oscillator device and system. The nanomechanical oscillator device comprises at least one nanoresonator, such as a suspended nanotube, designed such that injecting charge density into the tube (e.g. by applying a capacitively-coupled voltage bias) changes the resonant frequency of the nanotube, and where exposing the resonator to an RF bias induces oscillatory movement in the suspended portion of the nanotube, forming a nanoscale resonator, as well as a force sensor when operated in an inverse mode. A method of producing an oriented nanoscale resonator structure with integrated electrodes is also provided in the patent.
Here is proposed a fundamentally different nanotube resonator, which takes advantage of one of carbon nanotubes' most interesting properties. Multiwalled carbon nanotubes (MWNTs), which consist of multiple, concentric nanotubes precisely nested within one another, exhibit a striking telescoping property whereby an inner nanotube core may slide within the atomically smooth casing of an outer nanotube shell [CUMI 00a]. Already this property has been exploited to build a rotational nanomotor [FENN 03] and a nanorheostat [CUMI 04]. Future nanomachines such as a gigahertz mechanical oscillator are envisioned [ZHEN 02]. By harnessing this versatile telescoping property in a new fashion, a tunable nanoscale resonator has been developed.